At the LDA 2011 conference Faith Smith told us about her research project at Bristol University surveying pet dogs to estimate the prevalence of Lyme disease infected ticks. Her paper has just been published.
The random samples of ticks were from dogs inspected at veterinary surgeries across the UK. Samples positive for Borrelia burgdorferi, the bacteria that cause Lyme disease, were found in ticks from Scotland to the Southwest of England and other places in between.
This study was well designed and a large number of dogs surveyed across a very wide geographical area. The vets’ surgeries were not just in “hot spots” and were in towns as well as country areas. Dogs were inspected throughout the season of March to October. So this was a good attempt to get closer to the real numbers of infected ticks.
4 species of ticks were identified: The sheep tick (Ixodes ricinus), the hedgehog tick (I. hexagonus), the fox tick (I. canisuga) and the ornate cow tick (Dermacentor reticulatus).
Some ticks were too damaged to be tested for Borrelia, but of those that were tested, the ospA gene of Borrelia species was detected in 2.3%. The researchers did not identify the bacteria down to genospecies level, but their test would have detected all genospecies of Borrelia burgdorferi sensu lato, including the lesser studied ones.
Of the positive samples, 15 were from I. ricinus and 2 from I. hexagonus. No positive samples were found among the I. canisuga or D. reticulatus. The positive sample is too small to draw any conclusions on relative prevalence except that both the sheep tick and the hedgehog tick carry B. burgdorferi.
In total 3534 dogs were examined by the vets and 810 were carrying at least one tick. The sheep tick was identified in 72.1% cases, the hedgehog tick in 21.7% and the fox tick in 5.6% cases. Five samples of the ornate cow tick were also received by the researchers. None of the dogs with infected ticks had recently been abroad, so these were UK acquired ticks.
A previous study (Ogden et al 2000), using a different survey method, identified ticks collected from UK cats and dogs and found a higher proportion (39%) were hedgehog ticks. That study found that the hedgehog tick was more frequently carried by cats and the sheep tick by dogs.
What pet do you have?
Hedgehog ticks and fox ticks are not very often counted in surveys, as many surveys rely on blanket dragging over the ground in known countryside habitats for the sheep tick. Hedgehog and fox ticks (the latter also found on badgers) live in the burrows of their hosts but will sometimes drop off their host as it walks through a town garden or park.
Town dwellers, beware!
As LDA continues to point out, Lyme disease is not just a problem of a few countryside “hot spots”.
Visit our YouTube channel to see an interview with Faith Smith at the LDA conference in September 2011.